3.5.0: Parse AWS CLI command lines

Include command and subcommand in the output: "aws s3 sync" for example.

Before this release that would only have rendered as "aws".

This release also removes the dependency on python-dateutil, making the
binary much smaller.

3.4.1: pxtree: Properly handle no-matches

If you supply pxtree with a search pattern and there are no matches,
just print a message to that effect and list no processes.

3.4.0: Add a "pxtree" binary

It lists running processes in a tree, and supports a search parameter
just like px and ptop.

Also, for px, this release improves the default sort order:
https://github.com/walles/px/commit/723057b1ac84abd289d4901b71857e7d03dba331

3.3.1: Ignore terraform's -chdir switch

Now we render "terraform -chdir=dev apply" as "terraform apply" in the
output.

Also render "brew.rb" as "brew" in the output, as that's what the user
typed.

3.3.0: Show subcommands

Subcommands will now be shown for some commands. "go build" will be
shown by px / ptop as "go build" rather than just "go" for example.

The list of subcommand enabled binaries include "brew", "apt-get",
"git", "docker", "npm" and others.

3.2.0: Improve searching for short commands

Before this release, if you searched for a short command (either in px
or in ptop), the result tended to be drowned out in lots of unrelated
hits.

With this release in place, exact command matches get sorted to the most
prominent end of the list.

3.1.0: Introduce CPU bars

When the window is wide enough, two more bars will be visible at the top
of the screen.

The bars under RAM Use are the same as before, but the new ones under
Sysload show how CPU time is used up by different programs / users.

3.0.0: Improve Launches section height

Fixes <https://github.com/walles/px/issues/98>.

Additionally, this release also uses comparable units for RAM (current
vs max) and for IO Load (#97).

The new version number indicates that this release drops support for
Python 2, which has now been dead for over two years.

1.6.1: Add by-user RAM usage visualization

Also, on macOS, "Electron" processes now get named after the .app they
belong to. Issues #74 and #87 related to ruby command line parsing have
been fixed.

1.6.0: ptop: Visualize top memory using programs

Processes are grouped and summed by their names, so if you have multiple
Firefox processes their RAM use will be summed into one entry for the
purpose of this visualization.

See updated screenshot for details, it's on the same line as the RAM
numbers.